Alternaria tomatophila attacks all the aerial organs of the tomato at all stages of plant growth.

It affects young plants , before and after transplanting, in extensive wet and cold nurseries. In addition to damping-off , this fungus is the cause of more or less extensive black alterations on the stem, located near the crown or higher up. After girdling the stem, the lesions can quite quickly lead to the drying plants out and their death . Attacks at this stage of plant development are due to contamination of the seeds and / or soil in the nursery.

On adult plants , it mainly causes leaf spots that develop more on the low and mature leaves then progressing towards the apices. These spots are initially dark green , then quickly turn brown to black (Figures 1 to 3). They have a more or less rounded shape, sometimes angular when delimited by the ribs. Their diameter is often of the order of a centimeter, and can reach several centimeters when the climatic conditions are particularly favorable and / or when the spots merge. The latter have the characteristic of presenting discrete concentric patterns giving them the appearance of a target. They are located over the entire limbus, including its periphery. In the latter case, they do not always have concentric rings. A more or less bright yellow halo (due to the effects of a toxin) is sometimes visible around these spots which, eventually, end up necrosis. When there are many and the climatic conditions are very favorable, whole leaflets can turn yellow and dry out , sometimes leading to significant defoliation of the plants.

Of spots rather similar are also found on the rods (Figure 4), the petioles (Figure 5) and the stalks ; they have a tinge blackish and often have a more elongated shape. These lesions can surround the affected organ and cause dieback of its distal part.

On the fruits , concave spots well-defined appear near the stalk scar and sepals (Figures 6 and 7). The latter, colonized at first, are often altered. The surface of the spoiled areas of the fruit wrinkles; it can be covered with a black mold rather characteristic , velvety , and there are concentric patterns, as on the leaves. Both green and ripe fruits can be affected; those at advanced maturity are little or not affected. Note that contaminations can take place through injuries such as growth cracks. Lesions on fruits can cause them to drop in large quantities. Strong early blight attacks can also be the cause of a reduction in the size and number of fruits produced.

It should be noted that several aerial pests of tomato can cause symptoms on leaflets that can be confused with those caused by A. tomatophila , in particular Cristulariella moricola causes (Hino) Redhead (= C. pyramidalis Waterman & Marshall), a confidential fungus on this solanacea which large concentric spots ( zonate leaf spot ).